There are IDE CD/DVD emulators that are harddrive backed, and connect to a host pc for downloading the iso to the harddrive, thats about the closest thing I know of. That type of thing was used for the Xbox 1 development units. The Chihiro arcade units (an arcade board based off an xbox motherboard) used a maskrom disk that attached via IDE as well.
I guess you could do something similar to the HxC USB version, just change the interface to IDE (which should be a little bit simpler than floppy emulation, because seek commands on a harddrive have status codes that indicate when the data is ready for reading from the buffer). It would still require quite a bit of changes to the VHDL/Verilog sources for the chip.
I'm not sure if they even exist, but a iSCSI hba that plugs in asif it were a drive would be another option assuming you had a scsi controller in your amiga.
